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General Description
Section 1
1-52
that the user declare the member to be a tension only member
by using the MEMBER TENSION command, after the CABLE
command. This will ensure that the program will test the
nature of the force in the member after the analysis and if it is
compressive, the member is switched off and the stiffness
matrix re-calculated.
4) Due to potential instability problems explained in item 1
above, users should also avoid modeling a catenary by
breaking it down into a number of straight line segments. The
linear cable member in STAAD cannot be used to simulate the
behavior of a catenary. By catenary, we are referring to those
structural components which have a curved profile and develop
axial forces due to their self weight. This behavior is in reality
a non-linear behavior where the axial force is caused because
of either a change in the profile of the member or induced by
large displacements, neither of which are valid assumptions in
an elastic analysis. A typical example of a catenary is the main
U shaped cable used in suspension bridges.
5) The increase of stiffness of the cable as the tension in it
increases under applied loading is updated after each iteration
if the cable members are also declared to be MEMBER
TENSION. However, iteration stops when all tension members
are in tension or slack; not when the cable tension converges.